//===--- StringRef.h - Constant String Reference Wrapper --------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_ADT_STRINGREF_H
#define LLVM_ADT_STRINGREF_H

#include <cassert>
#include <cstring>
#include <utility>
#include <string>

namespace llvm {
template <typename T>
class SmallVectorImpl;
class APInt;

/// StringRef - Represent a constant reference to a string, i.e. a character
/// array and a length, which need not be null terminated.
///
/// This class does not own the string data, it is expected to be used in
/// situations where the character data resides in some other buffer, whose
/// lifetime extends past that of the StringRef. For this reason, it is not in
/// general safe to store a StringRef.
class StringRef {
public:
  typedef const char* iterator;
  typedef const char* const_iterator;
  static const size_t npos = ~size_t(0);
  typedef size_t size_type;

private:
  /// The start of the string, in an external buffer.
  const char* Data;

  /// The length of the string.
  size_t Length;

  // Workaround PR5482: nearly all gcc 4.x miscompile StringRef and std::min()
  // Changing the arg of min to be an integer, instead of a reference to an
  // integer works around this bug.
  static size_t min(size_t a, size_t b) { return a < b ? a : b; }
  static size_t max(size_t a, size_t b) { return a > b ? a : b; }

  // Workaround memcmp issue with null pointers (undefined behavior)
  // by providing a specialized version
  static int compareMemory(const char* Lhs, const char* Rhs, size_t Length) {
    if (Length == 0) {
      return 0;
    }
    return ::memcmp(Lhs, Rhs, Length);
  }

public:
  /// @name Constructors
  /// @{

  /// Construct an empty string ref.
  /*implicit*/ StringRef() : Data(0), Length(0) {}

  /// Construct a string ref from a cstring.
  /*implicit*/ StringRef(const char* Str) : Data(Str) {
    assert(Str && "StringRef cannot be built from a NULL argument");
    Length = ::strlen(Str); // invoking strlen(NULL) is undefined behavior
  }

  /// Construct a string ref from a pointer and length.
  /*implicit*/ StringRef(const char* data, size_t length)
      : Data(data), Length(length) {
    assert(
        (data || length == 0) &&
        "StringRef cannot be built from a NULL argument with non-null length");
  }

  /// Construct a string ref from an std::string.
  /*implicit*/ StringRef(const std::string& Str)
      : Data(Str.data()), Length(Str.length()) {}

  /// @}
  /// @name Iterators
  /// @{

  iterator begin() const { return Data; }

  iterator end() const { return Data + Length; }

  /// @}
  /// @name String Operations
  /// @{

  /// data - Get a pointer to the start of the string (which may not be null
  /// terminated).
  const char* data() const { return Data; }

  /// empty - Check if the string is empty.
  bool empty() const { return Length == 0; }

  /// size - Get the string size.
  size_t size() const { return Length; }

  /// front - Get the first character in the string.
  char front() const {
    assert(!empty());
    return Data[0];
  }

  /// back - Get the last character in the string.
  char back() const {
    assert(!empty());
    return Data[Length - 1];
  }

  /// equals - Check for string equality, this is more efficient than
  /// compare() when the relative ordering of inequal strings isn't needed.
  bool equals(StringRef RHS) const {
    return (Length == RHS.Length &&
            compareMemory(Data, RHS.Data, RHS.Length) == 0);
  }

  /// equals_lower - Check for string equality, ignoring case.
  bool equals_lower(StringRef RHS) const {
    return Length == RHS.Length && compare_lower(RHS) == 0;
  }

  /// compare - Compare two strings; the result is -1, 0, or 1 if this string
  /// is lexicographically less than, equal to, or greater than the \arg RHS.
  int compare(StringRef RHS) const {
    // Check the prefix for a mismatch.
    if (int Res = compareMemory(Data, RHS.Data, min(Length, RHS.Length)))
      return Res < 0 ? -1 : 1;

    // Otherwise the prefixes match, so we only need to check the lengths.
    if (Length == RHS.Length)
      return 0;
    return Length < RHS.Length ? -1 : 1;
  }

  /// compare_lower - Compare two strings, ignoring case.
  int compare_lower(StringRef RHS) const;

  /// compare_numeric - Compare two strings, treating sequences of digits as
  /// numbers.
  int compare_numeric(StringRef RHS) const;

  /// \brief Determine the edit distance between this string and another
  /// string.
  ///
  /// \param Other the string to compare this string against.
  ///
  /// \param AllowReplacements whether to allow character
  /// replacements (change one character into another) as a single
  /// operation, rather than as two operations (an insertion and a
  /// removal).
  ///
  /// \param MaxEditDistance If non-zero, the maximum edit distance that
  /// this routine is allowed to compute. If the edit distance will exceed
  /// that maximum, returns \c MaxEditDistance+1.
  ///
  /// \returns the minimum number of character insertions, removals,
  /// or (if \p AllowReplacements is \c true) replacements needed to
  /// transform one of the given strings into the other. If zero,
  /// the strings are identical.
  unsigned edit_distance(StringRef Other, bool AllowReplacements = true,
                         unsigned MaxEditDistance = 0);

  /// str - Get the contents as an std::string.
  std::string str() const {
    if (Data == 0)
      return std::string();
    return std::string(Data, Length);
  }

  /// @}
  /// @name Operator Overloads
  /// @{

  char operator[](size_t Index) const {
    assert(Index < Length && "Invalid index!");
    return Data[Index];
  }

  /// @}
  /// @name Type Conversions
  /// @{

  operator std::string() const { return str(); }

  /// @}
  /// @name String Predicates
  /// @{

  /// startswith - Check if this string starts with the given \arg Prefix.
  bool startswith(StringRef Prefix) const {
    return Length >= Prefix.Length &&
           compareMemory(Data, Prefix.Data, Prefix.Length) == 0;
  }

  /// endswith - Check if this string ends with the given \arg Suffix.
  bool endswith(StringRef Suffix) const {
    return Length >= Suffix.Length &&
           compareMemory(end() - Suffix.Length, Suffix.Data, Suffix.Length) ==
               0;
  }

  /// @}
  /// @name String Searching
  /// @{

  /// find - Search for the first character \arg C in the string.
  ///
  /// \return - The index of the first occurrence of \arg C, or npos if not
  /// found.
  size_t find(char C, size_t From = 0) const {
    for (size_t i = min(From, Length), e = Length; i != e; ++i)
      if (Data[i] == C)
        return i;
    return npos;
  }

  /// find - Search for the first string \arg Str in the string.
  ///
  /// \return - The index of the first occurrence of \arg Str, or npos if not
  /// found.
  size_t find(StringRef Str, size_t From = 0) const;

  /// rfind - Search for the last character \arg C in the string.
  ///
  /// \return - The index of the last occurrence of \arg C, or npos if not
  /// found.
  size_t rfind(char C, size_t From = npos) const {
    From     = min(From, Length);
    size_t i = From;
    while (i != 0) {
      --i;
      if (Data[i] == C)
        return i;
    }
    return npos;
  }

  /// rfind - Search for the last string \arg Str in the string.
  ///
  /// \return - The index of the last occurrence of \arg Str, or npos if not
  /// found.
  size_t rfind(StringRef Str) const;

  /// find_first_of - Find the first character in the string that is \arg C,
  /// or npos if not found. Same as find.
  size_type find_first_of(char C, size_t From = 0) const {
    return find(C, From);
  }

  /// find_first_of - Find the first character in the string that is in \arg
  /// Chars, or npos if not found.
  ///
  /// Note: O(size() + Chars.size())
  size_type find_first_of(StringRef Chars, size_t From = 0) const;

  /// find_first_not_of - Find the first character in the string that is not
  /// \arg C or npos if not found.
  size_type find_first_not_of(char C, size_t From = 0) const;

  /// find_first_not_of - Find the first character in the string that is not
  /// in the string \arg Chars, or npos if not found.
  ///
  /// Note: O(size() + Chars.size())
  size_type find_first_not_of(StringRef Chars, size_t From = 0) const;

  /// find_last_of - Find the last character in the string that is \arg C, or
  /// npos if not found.
  size_type find_last_of(char C, size_t From = npos) const {
    return rfind(C, From);
  }

  /// find_last_of - Find the last character in the string that is in \arg C,
  /// or npos if not found.
  ///
  /// Note: O(size() + Chars.size())
  size_type find_last_of(StringRef Chars, size_t From = npos) const;

  /// @}
  /// @name Helpful Algorithms
  /// @{

  /// count - Return the number of occurrences of \arg C in the string.
  size_t count(char C) const {
    size_t Count = 0;
    for (size_t i = 0, e = Length; i != e; ++i)
      if (Data[i] == C)
        ++Count;
    return Count;
  }

  /// count - Return the number of non-overlapped occurrences of \arg Str in
  /// the string.
  size_t count(StringRef Str) const;

  /// getAsInteger - Parse the current string as an integer of the specified
  /// radix.  If Radix is specified as zero, this does radix autosensing using
  /// extended C rules: 0 is octal, 0x is hex, 0b is binary.
  ///
  /// If the string is invalid or if only a subset of the string is valid,
  /// this returns true to signify the error.  The string is considered
  /// erroneous if empty.
  ///
  bool getAsInteger(unsigned Radix, long long& Result) const;
  bool getAsInteger(unsigned Radix, unsigned long long& Result) const;
  bool getAsInteger(unsigned Radix, int& Result) const;
  bool getAsInteger(unsigned Radix, unsigned& Result) const;

  // TODO: Provide overloads for int/unsigned that check for overflow.

  /// getAsInteger - Parse the current string as an integer of the
  /// specified radix, or of an autosensed radix if the radix given
  /// is 0.  The current value in Result is discarded, and the
  /// storage is changed to be wide enough to store the parsed
  /// integer.
  ///
  /// Returns true if the string does not solely consist of a valid
  /// non-empty number in the appropriate base.
  ///
  /// APInt::fromString is superficially similar but assumes the
  /// string is well-formed in the given radix.
  bool getAsInteger(unsigned Radix, APInt& Result) const;

  /// @}
  /// @name Substring Operations
  /// @{

  /// substr - Return a reference to the substring from [Start, Start + N).
  ///
  /// \param Start - The index of the starting character in the substring; if
  /// the index is npos or greater than the length of the string then the
  /// empty substring will be returned.
  ///
  /// \param N - The number of characters to included in the substring. If N
  /// exceeds the number of characters remaining in the string, the string
  /// suffix (starting with \arg Start) will be returned.
  StringRef substr(size_t Start, size_t N = npos) const {
    Start = min(Start, Length);
    return StringRef(Data + Start, min(N, Length - Start));
  }

  /// slice - Return a reference to the substring from [Start, End).
  ///
  /// \param Start - The index of the starting character in the substring; if
  /// the index is npos or greater than the length of the string then the
  /// empty substring will be returned.
  ///
  /// \param End - The index following the last character to include in the
  /// substring. If this is npos, or less than \arg Start, or exceeds the
  /// number of characters remaining in the string, the string suffix
  /// (starting with \arg Start) will be returned.
  StringRef slice(size_t Start, size_t End) const {
    Start = min(Start, Length);
    End   = min(max(Start, End), Length);
    return StringRef(Data + Start, End - Start);
  }

  /// split - Split into two substrings around the first occurrence of a
  /// separator character.
  ///
  /// If \arg Separator is in the string, then the result is a pair (LHS, RHS)
  /// such that (*this == LHS + Separator + RHS) is true and RHS is
  /// maximal. If \arg Separator is not in the string, then the result is a
  /// pair (LHS, RHS) where (*this == LHS) and (RHS == "").
  ///
  /// \param Separator - The character to split on.
  /// \return - The split substrings.
  std::pair<StringRef, StringRef> split(char Separator) const {
    size_t Idx = find(Separator);
    if (Idx == npos)
      return std::make_pair(*this, StringRef());
    return std::make_pair(slice(0, Idx), slice(Idx + 1, npos));
  }

  /// split - Split into two substrings around the first occurrence of a
  /// separator string.
  ///
  /// If \arg Separator is in the string, then the result is a pair (LHS, RHS)
  /// such that (*this == LHS + Separator + RHS) is true and RHS is
  /// maximal. If \arg Separator is not in the string, then the result is a
  /// pair (LHS, RHS) where (*this == LHS) and (RHS == "").
  ///
  /// \param Separator - The string to split on.
  /// \return - The split substrings.
  std::pair<StringRef, StringRef> split(StringRef Separator) const {
    size_t Idx = find(Separator);
    if (Idx == npos)
      return std::make_pair(*this, StringRef());
    return std::make_pair(slice(0, Idx), slice(Idx + Separator.size(), npos));
  }

  /// split - Split into substrings around the occurrences of a separator
  /// string.
  ///
  /// Each substring is stored in \arg A. If \arg MaxSplit is >= 0, at most
  /// \arg MaxSplit splits are done and consequently <= \arg MaxSplit
  /// elements are added to A.
  /// If \arg KeepEmpty is false, empty strings are not added to \arg A. They
  /// still count when considering \arg MaxSplit
  /// An useful invariant is that
  /// Separator.join(A) == *this if MaxSplit == -1 and KeepEmpty == true
  ///
  /// \param A - Where to put the substrings.
  /// \param Separator - The string to split on.
  /// \param MaxSplit - The maximum number of times the string is split.
  /// \param KeepEmpty - True if empty substring should be added.
  void split(SmallVectorImpl<StringRef>& A, StringRef Separator,
             int MaxSplit = -1, bool KeepEmpty = true) const;

  /// rsplit - Split into two substrings around the last occurrence of a
  /// separator character.
  ///
  /// If \arg Separator is in the string, then the result is a pair (LHS, RHS)
  /// such that (*this == LHS + Separator + RHS) is true and RHS is
  /// minimal. If \arg Separator is not in the string, then the result is a
  /// pair (LHS, RHS) where (*this == LHS) and (RHS == "").
  ///
  /// \param Separator - The character to split on.
  /// \return - The split substrings.
  std::pair<StringRef, StringRef> rsplit(char Separator) const {
    size_t Idx = rfind(Separator);
    if (Idx == npos)
      return std::make_pair(*this, StringRef());
    return std::make_pair(slice(0, Idx), slice(Idx + 1, npos));
  }

  /// @}
};

/// @name StringRef Comparison Operators
/// @{

inline bool operator==(StringRef LHS, StringRef RHS) { return LHS.equals(RHS); }

inline bool operator!=(StringRef LHS, StringRef RHS) { return !(LHS == RHS); }

inline bool operator<(StringRef LHS, StringRef RHS) {
  return LHS.compare(RHS) == -1;
}

inline bool operator<=(StringRef LHS, StringRef RHS) {
  return LHS.compare(RHS) != 1;
}

inline bool operator>(StringRef LHS, StringRef RHS) {
  return LHS.compare(RHS) == 1;
}

inline bool operator>=(StringRef LHS, StringRef RHS) {
  return LHS.compare(RHS) != -1;
}

inline std::string& operator+=(std::string& buffer, llvm::StringRef string) {
  return buffer.append(string.data(), string.size());
}

/// @}

// StringRefs can be treated like a POD type.
template <typename T>
struct isPodLike;
template <>
struct isPodLike<StringRef> {
  static const bool value = true;
};

} // namespace llvm

#endif
